Method of distiling tar and apparatus therefor



S. P. MILLER Aug. 28, 1934.

METHOD OF DISTILLING TAR AND APPARATUS THEREFOR Filed March 23, 1928 5Sheets-Sheet 1 ATTORNEYS S. P. MILLER Aug. 28, 1934.

METHOD OF DISTILLING TAR AND APPARATUS THEREFOR Filed March 23, 1928 5Sheets-Sheet 2 (a/re Oren I Illllllllllllllll a :frli imzz QQQG QQ INVENOR w izzu MM ra -A ATTORNEY5 S. P. MILLER Aug. 28, 1934.

METHOD OF DIST ILLING TAR AND APPARATUS THEREFOR Filed March 25, 1928 5Sheets -Sheat 3 INVENTOR WW ATTORNEYS S. P. MILLER Aug. 28, 1934.

METHOD OF DISTILLING TAB. AND APPARATUS THEREFOR Filed March 23, 1928 5Sheets-Sheet 4 ATTORNEY5 Aug 28, 1934. s.. P. MILLER 1,971,690

METHOD OF DISTILLING TAB AND APPARATUS THEREFOR Filed March 23, 1928 sSheets-Sheet 5 INVENTOR ATTORNEYS Patented Aug. 28, 1934 PATENT OFFICEMETHOD OF DISTILLING TAB AND APPARATUS THEREFOR Stuart Pal-melee Miller,Englewood, N. J., as-

signor to The Barrett Company, New York, N. Y., a corporation of NewJersey Application March 23, 1928, Serial No. 263,988

6 Claims. (Cl. 202-30) This invention relates to improvements in thedistillation of pitch, tar and tar oils and includes a new method ofdistillation as well as an improved apparatus therefor. The invention isapl plicable to the distillation of pitch, tar or tar oil with othercoal distillation or gasification gases, but will be more particularlydescribed as applied to coke oven and gas retort operation.

In the ordinary operation of by-productcoke l ovens, the gases producedby the coking operation pass from the individual ovens thru uptake pipesand goose-necks to a collector main common to the ovens of the battery.The gases, commonly known as foul gases, leave the ovens 5 at hightemperatures, for example at 600 to 700 C., or higher, and carry aconsiderable proportion of volatilized tars and oils as well as solidparticles of coke, dust, etc. Ordinarily the gases are cooled by theapplication of sprays or ammonia liquor or ammonia liquor and tar in thecollector main, the heat in the gases being thereby dissipated and lost.In some cases sprays are not used but large quantities of tar or tar andammonia liquor are flushed along the bottom of the main. The rapidcooling causes separation of tar containing heavier oils in thecollector main. Further cooling is effected in the cross-over main whichconnects the collector main to the condensing system and an additionalquantity of tar carrying both heavy and lighter oils is thus separated,In the condensers additional quantities of tarry oils are recovered andare commonly blended with the heavier tars from the collector main.

The collected tar is ordinarily shipped from the coke oven or other coaldistillation plant to a tar distillation plant for distillation andseparation of the oils, and the production of pitches of varyingquality. Handling costs, freight charges and distillation costs andlosses, including fuel, capital and maintenance expense for the specialequipment required for distillation, add to the cost of the tardistillation products.

The present invention provides an improved method and apparatus fordistilling pitch, tar or oil by means of hot coal distillation orcarbonization gases such as gases from coke oven operations supplementedby heat externally applied during the distillation. The presentinvention makes use of heat contained in high temperature coaldistillation gases by employing them, while still at a high temperature,for distilling the pitch tar or oil in stills while heating the stills,or equipment thru which the gases pass on their way to the stills,externally by means of waste flue gases, or other heating gases or bysteam whereby distillation is effected in part by direct contact withthe hot coal distillation gases, and in part by externally applied heat.

Several circumstances may arise which will make it desirable to heatexternally, as when the heat otherwise available is insufficient toraise the contents of the still to the required temperature, or it maybe desirable to apply heat externally in order to increase the capacityof the still and to supplement the distilling effect of the hot coaldistillation gases.

The material to be distilled according to the present invention may becoal tar produced at coke oven plants, or gas house tar produced at gas7 retort plants (vertical, horizontal or inclined), water gas tar, ortar or oil from another source. Pitches may likewise be distilled.- Suchtars frequently contain a considerable percentage of wa-- ter intimatelyadmixed or combined therewith, particularly where water or ammonialiquor is employed for condensing and separating the tar constituentsfrom the coal distillation or other gases; and such tars may if desiredbe dehydrated before being distilled according to this invention. Thegases which are employed, according to the present invention, for thedistillation are hot gases produced by a coal carbonization orgasiflcation operation, such as hot coke oven or gas retort gases, orhot water gas. These gases are brought 35 into direct contact with thematerial to be distilled, and the heat thus supplied is supplemented byexternal heating of the still or other apparatus in which thedistillation is carried out. The hot coal distillation or gasificationgases may be hot coke oven gases or hot gas retort gases or hot watergas, etc. In the case of coke oven gases, for example, the gases escapefrom the coke oven at a high temperature, for example from 600 to 700 C.or even higher in some cases. High temperature gases are also formed andare withdrawn from gas retorts, water gas retorts, producers, etc.

The external heating of the still or scrubber, etc., in which thedistillation is effected, may be by hot flue gas, or by the combustionof the fuel gas remaining after the removal of other valuable productsfrom the coal distillation gas, or other products of combustion may beemployed, or steam may be used. Although the invention is of broaderapplication, it will be described particularly in connection with cokeoven operation. The gas employed for the distillation by direct contactwith the tar or oil, may be withdrawn at practically its maximumtemperature as it comes from the coke oven, or the gas may be employedat a somewhat lower temperature. The temperature of the gas may beregulated by the treatment to which it is subjected prior to its use inthe distillation operation. If it is not desired to use the gas at amaximum temperature it may be sprayed with ammonia liquor in thegoose-neck or in the collector main, or it may be sprayed with tar oroil in the gooseneck or in the collector main, or it may be sprayed witha mixture of the two, or in both the goose-neck and collector main, tocool it to a regulated temperature.

Due to the great specific heat and heat of vaporization of water,spraying with water or ammonia liquor produces a greater cooling effecton the gases than spraying with an equal amount of tar. By regulatingthe quantity of the water and/or tar sprayed into the gases, thetemperature of the gases can be controlled. The temperature of the gasesmay likewise be controlled by regulating the temperature of the spray.Thespray may be sufficient to prevent the accumulation of solid hardpitch, etc., in the collector main.

Such accumulation can largely be avoided by eliminating the sprays andflushing the bottom of the main with a large quantity of ammonia liquoror tar without corresponding reduction in gas temperature.

The temperature and amount of the coal carbonization or gasificationgases used and the amount of heat applied externally may be regulatedaccording to the distillation which is to be carried out and will dependupon the character and quantity of oil to be distilled.

By heating the still or other parts of the equipment externally, eitherby the combustion of fuel gases or other combustible material, or byheating by means of what would otherwise" be waste heat, as by utilizingthe heat of the flue gases, or by employing steam, the desireddistillation may be accomplished in the still with coal distillationgases of lower temperature and/or with a smaller quantity of coaldistillation gases than would otherwise be necessary.

The vapors driven off from the still as well as the gases employed forthe distillation are advantageously admixed with the hot gases comingdirectly from the coke oven so that the vapors produced by thedistillation will be condensed and the oils recovered along withcondensed oils from vapors normally contained in such gases.

In the operation of a coke oven, the gases produced during one ovencycle, are not of uniform composition. At the start of the coaldistillation process, oils, etc., are liberated from the coal in largequantities and the first gases given off are rich in volatile products.The gases given off during the latter part of the distillation, forexample during, approximately, the last thirty percent of the operatingtime under normal conditions, contain a less percentage of condensableconstituents than the richer gases given off during the first part ofthe distillation, and are designated as lean gases. The tars carried inrich gases contain lower percentages of free carbon than do the tarscontained in lean gases,

and the lean gases carry lower percentages of total tar than do the richgases. There is in many cases an advantage in using either the richgases or lean gases separately in distillation of tar, oil or pitch,according to the present invention. For example, lean gases are capableof taking up a greater quantity of oil vapors per unit volume than anequivalent amount of a "rich gas which already contains more volatilecondensable constituents than does the lean gas,

the temperature being the same in each case; while rich gases contain alarger amount of condensable oil vapors which admix with the distilledoil vapors and are condensed therewith. In order to take advantage ofeither rich or lean gas, the coke oven may be equipped with twocollector mains, each of which is adapted to be thrown intocommunication with the uptake pipe from each of the ovens in the batteryto which the collector mains are connected thru a system of valves. Asan example, during the first of the distillation operation in any oneoven, this oven will be thrown into communication with the collectormain which is connected directly with the usual recovery apparatus.After the distillation has progressed to the point where lean gases arebeing given off in this oven, it will be thrown into communicationwith'the other collector main which is in communication with the still.By the usual rotation of the ovens in a battery of average size, therewill at all times be a fairly continuous and uniform production of leangases, so that the quantity and temperature of the gases passing thruthe still will be fairly uniform at all times. Rich gases are, in manycases, more desirable for distillation, and can in a similar manner, beutilized by my invention.

Carrying out the distillation according to the present ,invention, thehot coal distillation gases are brought into heat-interchanging relationwith the tar or oil to be distilled and are advantageously brought intodirect and intimate contact with the oil or tar or pitch while at thesame time heat is being externally applied to some part of theapparatus. Intimate contact of the pitch, tar or oil and gases can beeffected in various ways, and the distilling operation can be carriedout either as a batch operation or as a continuous operation. The pitch,tar or oil to be distilled can, for example, be atomized or sprayed intoa current of the hot gas, thereby bringing the pitch, tar or oilparticles into intimate contact with the hot gas and heating them to therequired temperature to effect distillation. Instead of spraying oratomizing the oil, tar or pitch into a current of hot gas, a current ofthe gas may be forced or drawn thru a body of material to be distilled,thereby heating and agitating it and effecting distillation of thedesired constituents therefrom, which vaporized constituents are carriedaway by the escaping gases. The material in the still can likewise beagitated or sprayed into the gases in the still by me chanical agitationor atomizing devices.

The distillation can likewise be effected in a counter-current manner,for example, by causing the pitch, tar or oil to be distilled to flowdownwardly thru a baffie tower or other apparatus in which an upwardflow of the hot gases is effected, so that the downwardly flowing pitch,tar or oil is progressively heated and distilled, or the hot gases maybe passed over the surface of a body of oil, tar or pitch, for instancein a closed tank. In this case, it will be desirable, though in manycases not essential, to agitate the contents of the tank to keep freshsurfaces exposed to the gases.

Several stills may be employed in series so that the gases leaving onestill will pass thru another still in which available heat of the gasesmay be used for distillation. Fresh pitch, tar or tar oils may besupplied to each still, or the residue from one still may be supplied tothe next still in the series, in which case it may be desirable to passthe material to be distilled and the gases thru the stills in oppositedirections so as to benefit by the advantages of countercurrentoperation. The gases may be scrubbed before entering the first still ofthe series, or the contact between the gases and the contents of thestill may serve to scrub impurities from the gases so that the gasesleaving the last still of the series ,will be relatively free fromimpurities, but will contain. oils which can be condensed by cooling thegases, and recovered as clean oils.

The usual spraying treatment to which the gases are subjected in thecollector main effects a partial scrubbing and cleaning of the gases,and heavy pitches and tar containing free carbon are thrown down in thecollector main 1! gases at lower than maximum temperature are to beused. The temperature of the gases prior to entering the stillcontaining the material to be distilled is regulated preferably bycontrolling the spraying to which the gases are subjected in thecollector main. This spraying may be designed to accomplish the doublepurpose of both regulating the temperature and cleaning the gases to agreater or to a less extent. In case gases at maximum temperature are tobe employed no sprays at all will be employed but tar or ammonia liquorwill be flushed along the bottom of the collector main.

The employment of hot coal distillation gases for the distillation ofthe pitch, tar or oil presents the advantage among others that the gasesthemselves are subjected to a scrubbing and purifying treatment bybringing them into contact with the pitch, tar or oilto be distilled,while the vapors of the volatile constituents, driven off by thedistillation, are admixed with the gases and their normally containedcondensable vapors and can be recovered therefrom in the same recoveryapparatus as used for cooling of the gases from the ordinary collectormain, or separate recovery apparatus may be provided.

As a result of this scrubbing action, the impurities in the gasescomprising both solid and liquid particles, are in partremoved from thegases and are recovered in the non-volatilized residue in the still. Thegases leaving the collector main in the ordinary operation of a cokeoven contain fine globules of tar or pitch, as well as solid particlescomprising dust, free carbon,

coke braize, etc., and the removal of such entrained materials from thegases and the recovery of them in the residue in the still may beundesirable as where relatively clean oil is being distilled and it isdesirable to produce a residue of low free carbon content in the still.To clean the gases, they may be scrubbed with tar, etc., or cleaned asby an electrical precipitator prior to entering the still. The scrubbingof the gases to clean them may, depending upon the result desired, bewith pitch, heavy tar, light tar or oil, either with more or lessdistillation, or without such distillation, and the temperature of thescrubbing medium can be regulated. Where the gases are to be scrubbedwithout cooling or distillation, the scrubbing medium should be '0 acomposition and temperature similar to that of the particles of pitchcarried by the gases. The gases can also be cleaned without lowering oftemperature by means of an electrical precipitator, suitably insulatedor heated. Where scrubbing is employed the scrubbing may be accomplishedin anyone of numerous devices designed for scrubbing gases. The ordinarytype of tower scrubber may be used.

The scrubbing of the gases alter leaving the collector main, but beforeentering the still, may be effected by the tar or pitch residue from thestill or by other suitable scrubbing medium. The

temperature and character of the scrubbing liquid is regulated so thatthe temperature of the gases entering the still is that desired for thedistillation which is to be accomplished in the still. In order tomaintain the gases entering the still at a sufliciently hightemperature, it may be necessary at times to pre-heat the scrubbingliquid. This maybe done by passing the liquid in heatinterchangingrelation with hot gases resulting from the distillation process or byapplying steam or other heat to the pipes leading to the scrubber.

Under certain conditions when the gases are scrubbed prior to beingpassed into the still it may be desirable to heat the gases as they passthru the scrubber rather than to apply heat externally to the still.This may be done by equipping the scrubber with a jacket and passing hotgases, such as flue gases, steam, etc. thru this jacket. Heat may beapplied to the scrubber in order to prevent the condensation of the lowboiling constituents of the gases in the scrubber as well as to supplyadditional heat for the distillation in the still. In certain cases itwill be desirable to heat both the scrubber and the still externally.

Depending upon the extent to which the distillation of the pitch, tar oroil is carried, substantially only the low boiling oils may be removedfrom the body of pitch, tar or oil, leaving a heavy pitch, a heavy taror light pitch or heavier oil residue in the still, or by carrying thedistillation further, heavier constituents will be volatilized andrecovered from the gases, and a heavier oil residue, tar or pitch willremain as a residue in the still.

The distillation can be accomplished in numerous ways. For example, alarge volume o1. relatively low temperature gases may be used, or asmaller volume of relatively high temperature 12) gases may be used. Thetar may be preheated if desired before being brought into contact'withthe gases.

The gases escaping from the distilling operation will carry in vaporform the constituents volatilized from the pitch, tar or oil and willcontain in addition thereto such of the vapor constituents carried bythe gases entering the still as have not been removed by condensation orby contact with the material being distilled. In the case of hot cokeoven gases employed for the distillation of coal tar produced by thecoke ovens, the hot gases after the distillation operation will containuncondensed constituents from the coal distillation as well as addedvapor constituents driven off from the coal tar during the distillation.

The gases from the still can be treated for the condensation andrecovery of the desirable constituents contained therein as well as forthe recovery of ammonia and. light oils'carried thereby. Where only aportion of the gases from the coal carbonization apparatus are passedthru the still, those gases which are enriched by passing thru the stillcan be treated in a separate recovery system and the oils condensedtherefrom will be a mixture of the oil constituents normally in thegases and those added to the gases during the distillation, whereas thecondensate from the remainder of the system will contain only the usualcondensable coal distilla- 150 tion products. The gases can, wheredesired, be treated in the same recovery system with the re malnder ofthe gases produced by the coal distillation.

In a coke oven plant where several batteries of coke ovens are operated,the rich or lean or normal gas from one battery may be employed fordistilling tar from the other batteries, or a part of the gases from onebattery may be so employed.

The gases used in theadistillation may be only a portion of the gasescollected in the collector main and may be taken off one end of thecollector main or all the gases passing thru the collector main may beutilized by taking them off the center-box according to the customarypractice. A pitch, tar or oil, other than a coal tar product, can bedistilled and the condensable constituents recovered in a separaterecovery system without contaminating the balance of the coal tarproducts produced from the remainder of the system.

Where the distillation is carried out as a batch operation, for example,by forcing hot gases thru the material to be distilled, it isprogressively heated by the hot gases and the lighter constituents areprogressively removed therefrom until the distillation has been carriedto the desired point, after which the operation can be discontinued, andthe residue withdrawn, and the still recharged with iurther tar or oilto be distilled. In the case of continuous distillation, the

operation can be controlled by regulating the time of contact of thepitch, tar or oil with the gases, or the intimacy of the contact, or thetemperature of the gases, or the amount of the gases or the extent ofthe external heating so that the desired degree of distillation can beeffected.

In some cases it may be desired to regulate the character of the residueof distillation or of scrubbing, as respects free carbon content or asrespects type of oils remaining in or added to it. This may to a greateror less extent be accomplished by using rich or lean or intermediategases for distillation. Rich gases contain tar with a relatively lowfree carbon content and they contain also oils of lower average boilingpoint and lower specific gravity than do lean gases. Rich gases containa greater amount of tar than do lean gases. As the gases get leaner, theamount of tar contained decreases, the percentage of free carbon in thetar increases, the amount of oil contained decreases and its specificgravity and average boiling point increase. Since in the scrubbing anddistillation operations more or less of the tar contained in the gaseswill be retained in the scrubbing or distillation residue and more orless of the contained heavy oils will be condensed and retained in theresidues, the character of the residues may to some extent be controlledby choosing the proper gases for distillation. Such gases may be rich,lean or intermediate gases.

The invention will be further described in connection with theaccompanying drawings illustrating several forms of apparatus embodyingthe invention and adapted for the practice of the process of theinvention, but it is intended and will be understood that the inventionis illustrated thereby but is not limited thereto.

In the accompanying drawings,

Fig. 1 shows in a somewhat conventional and diagrammatic manner a planview of a coke oven battery showing apparatus for the distillation oftar or a tar oil or pitch by direct contact with hot coke oven gases;and indirect contact with hot flue gases.

Fig. 2 is a sectional elevation of the apparatus of Fig. 1;

Fig. 3 is a plan view of a modified form of apparatus in which twocollector mains are shown together with separate apparatus for scrubbingthe hot gases and means for heating the still;

Fig. 4 is a detail showing an elevation of the scrubber;

Fig. 5 is an enlarged detail showing in crosssection the relation of thetwo collector mains of Fig. 3 to each other and the coke oven;

Fig. 6 is an elevation partly in cross-section showing in greater detailthe still shown in Fig. 1;

Fig. 7 is a cross-section of the still shown in Fig. 6 showing thejacket;

Fig. 8 is a plan view of the still shown in Fig. 6;

Fig. 9 shows a modified form of still which may be substituted for thestill shown in the precedin figures; and

Fig. 10 shows another form of still.

In the drawings, part of the coke oven battery is shown at 1 with theusual uptake pipes 2 for the escape of the coke oven gases, and theusual collector main 3 connected with the uptake pipes. The usualcenter-box for the collector main is shown at 4. The coke oven gasesescape from the collector main and the center-box thru the cross-overmain 5 to the cooling and condensing system indicated conventionally astwo condensers 7 and 8. From these condensers the gases pass thru thepipe 9 and the usual tar trap (not shown) to the exhauster 10, andthence thru the gas outlet pipe 25 to the tar extractor, ammonia andlight oil scrubbers, etc. (not shown).

In the collector main and goose-neck sprays 6 are provided forregulating the temperature of the gases and for scrubbing the gases moreor less and for flushing the collector main. The liquor admitted to thecollector main, which is not volatilized, together with the condensedtar, flows to the center-box 4 and together with the gases, carryingsome entrained tar and liquor and uncondensed vapors, passes over thruthe cross-over main 5 to the inlet of the condensers '7 and 8. At thatpoint the condensed tar and the liquor are diverted to decanter 12, thegases passing into the condensers 7 and 8.

The uptakes and collector main may be sprayed in the usual manner withammonia liquor thru the line 5'. When it is desired to spray the gasesin the whole or a portion of the collector main with tar, the valves inthe line feeding the sprays should be properly adjusted and tar suppliedthru the line 7'.

If it is desired to use the gases at approximately their maximumtemperature, it may be desirable to cut off partly or entirely thesprays in the sections of the main from which the gases are withdrawn.In such a case ammonia liquor and/or tar may be flushed into the main 3thru lines 3' and 8'. This flushing will assist in preventingaccumulation of hard pitch in the main 3.

An outlet pipev 11 may also be provided leading from the center-box 4for the tar and ammonia liquor which may, if desired, be conveyedtherethru to the decanter 12, where separation of the tar and ammonialiquor takes place. The tar, after such settling and separation, can beconveyed from decanter 12, either continuously or intermittently thru apipe 6' controlled by a valve 13' to the still 13. Valve 12' controlsthe flow of tar from the decanter 12. Tar from decanter 12 may be led tothe still by line 10', pump 40 and lines 39' and 6'. A gas pipe 14,which may be provided with insulation (not shown), leads, preferably,from one end of the collector main 3 to the still 13 and terminates, forexample, in a cross pipe 15 therein having perforations along its bottomside as best illustrated in Fig. 6. A valve 4 is provided in the pipe14. The gas escapes from the still to the pipe 16 having valve 20therein. The gases with admixed vapors may pass thru the pipe 16 and thevalve 20 to the separate condensers 22 and 23 where condensation ofvapors takes place and then thru a gas outlet pipe 19, having a valve 17therein, and a pipe 24 to the main gas outlet pipe 25. An exhauster 21is provided between the pipes 19 and 24 to draw oil the gases thru thestill 13 and the condensers 22 and 23. The exhauster may also be placedin pipe 14. A by-pass 18 having a valve 18' therein permits the gas topass around the condensers when the valves 20, 17 and 18' are properlyadjusted. The gases from the still may be carried to the cross-over main5 thru a pipe 21 controlled by a valve 22' for admixture with theordinary coke oven gases so that condensable constituents contained inthese gases from the still may be recovered in the main recovery system.

The residue of the tar or pitch from the still 13 passes thru the pipe26 and may be delivered by pump 27 either thru the pipe 28 to the tank30 or thru the pipe 31 to the tank 33, valves 29 and 32 being providedto control the flow thru these pipes.

Tar or tarry oils collected in the condensers and 8 can be withdrawnthru pipes 34 and 35 and delivered thru a pipe 36 controlled by valve 37to a decanter 38. The tar or tarry oils are separated therein from theammonia liquor and can be drawn oil to storage or delivered thru a .pipe39 controlled by a valve 40 thru pump 40' to the still 13.

In the apparatus illustrated in Figs. 1 and 2, the by-product recoverysystem of the coke oven battery can, for the most part, be operated inthe ordinary way, but a part of the hot coke oven gases are drawn offand employed for the distillation of tar, and these gases and containedvapors are then subjected to separate condensation or are returned foradmixture with the main coke oven gases for condensation therewith.

. The still may be heated externally in any suitable manner, as withburners supplied with fuel gas. In the drawings, the still is providedwith a jacket thru which waste flue gases are circulated. By adjustingthe damper 41' in the flue 41 or valve 42', any desired quantity of theflue gases may be diverted thru the by-pass 42 into the setting 15enclosing the whole or a portion of the still 13, and the desired amountof heat thereby added to the still. The external heating of the still inthis way aids and supplements the distilling eifect of the hot gasespassed directly into contact with the tar in the still.

In the collector main the coke oven gases may, when they are to be usedat less than maximum temperature, be subjected to regulated cooling bythe spray of ammonia liquor, or tar when used, and the current of tarand ammonia liquor flowing therethru. Where this spray would cool the.

gases to a temperature below that desired for distillation, the ammonialiquor or tar spray may be substantially reduced at the end of the mainfrom which the hot gases are withdrawn, or may even be omitted, so thatthe gases will pass thru the uptake pipes and into the end 0! the mainand thru the pipe 14 at a temperature not greatly below that at whichthey enter the-collector main. In this way, the gases can be employed ata high temperature at which they have a high distilling capacity. Byregulating the amount of ammonia liquor and tar sprayed into the end ofthe collector main from which the gases are taken, the temperature ofthe gases can be regulated. In general, it will be advantageous to drawoff the hot coke oven gases while they are still at a high temperature,subjecting them to little or no spraying, so as to obtain effectiveheating and distillation of the material in the still.

During the intimate contact 01' the hot coke oven gases with thecontents of the still, the gases will be scrubbed and purified to agreater or less extent from entrained tar and from heavy condensableconstituents, leaving in the gas proportionately more of the lightercondensable constituents, while the distillation of the tar or oil inthe still will drive off from the tar or oil the constituents, volatileunder the conditions, which will be admixed and carried along with thegases from the still, producing gas enriched in condensable oils. Thepercentage of free carbon and other impurities in the enriched gas will,as respects the contained condensable constituents, be relatively lessthan in unenriched gas. By subjecting the gases escaping from the stillto separate 5 cooling and condensation, a relatively clean oil can bedirectly obtained as in the decanter 23', while by returning the gasesand admixed vapors to the main condensing system the condensableconstituents can be recovered, as in decanter 38, without the need ofseparate condensing equipment, and the resulting products will berelatively cleaner than those normally obtained.

The apparatus shown in Fig. 3 discloses means whereby the richer gasesgiven oi! from the coke ovens may be collected separately from theleaner gases by means of two collector mains 342 and 343. Althougheither rich or lean gases may be used for distillation, in the apparatusillustrated lean gases are utilized. It is intended and is to beunderstood that the apparatus is equally adapted for utilizing richgases and conducting lean gases to the ordinary condensers 307 and 308or for using only part of the rich or lean gases for distillation.

By proper regulation of the valves 342 and 343', shown in Figs. 3 and 5,the gases evolved during the first of the distillation process may beled to therich collector main 342, whereas the lean gases evolved duringthe latter part of the 13Q distillation, may be collected in the leancollector main 343. Because of the fact that these lean gases are poorerin condensable oils, they are in many cases better adapted for use indistillation, and, therefore, according to one method 01' operation,they are separately collected as in the main 343 and led to the still tobe used for distillation, whereas the rich gases are collected in themain 342 and cooled and led to condensers in the usual manner. Likewise,if desired, the main 343 may be used as a rich gas main and the richgases used for distillation. In many cases this will be desirable.

Whereas the collector main 342 for the richer gases may be operatedaccording to the usual practice, the operation of the lean collectormain should be so regulated by adjusting the sprays of tar and/ orammonia liquor as to give adequate flushing of the main, with onlylimited cooling, so that the temperature of the lean gases leaving thecollector main is sumciently high in spite of the loss of heat involvedin passing to the still to eflect distillation in the still. Thecollector main my be sprayed with tar thru the line 307'. In some casesit may be advisable to eliminate part or all of the spraying in main343. In such a case the ammonia liquor and/or tar may be flushed intothe main 343 thru lines 345' and/or 360'. The gases are led oil from thelean collector main and passed thru the valve 341' to the scrubber 341and the purified gases are led thence thru the pipe 314 to the still313. The scrubber may in some cases be omitted. The material in thestill may be circulated by means of the pump 344 thru the pipe 345 andthus fed thru the sprays 346 to the scrubber and back to the still thruline 360, or it may pass thru line 349 to storage 350, or the scrubbermay be fed with tar or tarry oil by means of the pump 347 thru the pipe348 from the decanter 338. The still distillation residue together withthe unvolatilized constituents from the scrubber is led thru the pipe349 to the storage 350, or thru the pipe 351 to the storage receptacles330 and 331.

The operation of the scrubber will in general depend upon the desiredelimination of entrained material from the gases prior to their entryinto the still.

If, for example, it is desired to maintain the residue in the stillrelatively free from contamination by the materials entrained in thegases from the collector main, the scrubber will be operated and thescrubbing liquid leaving the scrubber will be delivered to separatestoragee. g., tank 350. In such a case an appropriate scrubbing liquidcan be used,-e. g., a small amount of the residue in the still, oroutside liquid, or a separate insulated tank (not shown) of material ofcomposition similar to the composition of the entrained liquids in thegases may be maintained, and the contents of the tank continuallyre-circulated thru the scrubber.

The degree of distillation accomplished in the still will depend uponnumerous factors among which are, the quantity of gas drawn thru thestill, the temperature of the gas, the amount of heat suppliedexternally to the still, the boiling range of the oils to be distilled,and the character of the liquid employed for scrubbing the gases.

The liquid used for scrubbing may in some cases be distilled. This willparticularly be the case when light tar or tarry oil such as that from338 or 338' is employed. When distillation of the scrubbing liquidoccurs, the temperature of the gases will tend to fall, due toabsorption of heat as latent heat of evaporation of the oils distilled.The tendency to drop in gas temperature may be oilset by the use of heatinterchanger 346' for preheating the scrubbing liquid, or by theaddition of heat thru jacket 351', or by both. The quantity of gas mayalso be increased.

It will thus be seen that there are numerous ways to accomplish thedesired results.

In some cases it will be desired to so thoroughly remove entrainedmaterials from the gases that the oils condensed in condensers 323 and322 will be relatively free from contamination by the entrainedmaterials, although the presence of the entrained materials in the stillresidue may be unobjectionable. In such a case, it will be of particularadvantage to recirculate the material in the still thru the scrubber andback to the still. The minimum of heat will be wasted and the gases willbe satisfactorily scrubbed. The heat in the gases entering the scrubberwill in such a case be allowed to accomplish distillation in thescrubber as well as in the still. If two oil fractions from condensers322 and 323 are desired the second fraction may be withdrawn thru line322' to decanter (not shown).

The scrubber or the still, or both the scrubber and the still, may beheated externally, as for example, by the combustion of fuel gases or byflue gases. Fig. 3 provides for heating with flue gases. By propermanipulation of the valves in the flues and the exhauster 340 whennecessary, circulation of the flue gases thru the pipes 349 and 350' andjacket 351' around the body of the scrubber, as well as thru the setting315' of the still, may be controlled.

The tar from either or both of the collector mains may be supplied thruthe pipe 352 to the still 313, or it maybe used to scrub the gases inthe scrubber, in which case it is pumped to the sprays 346 thru the pipe354. The line leading to the sprays may be equipped with a preheater346'.

The scrubber 341, as shown in Fig. 4 may consist of a tower with means314' at the bottom for admitting gases and means 314 at the top forleading them away. The scrubber is provided with sprays 346 for sprayingthe contents with tar or oil. It may be packed with broken brick orRaschig rings, etc.

With appropriate modification, the operation of the apparatus shown inFig. 3 is similar to that described in connection with Figs. 1 and 2.Tar from either of the collector mains or the decanters 338 and 338 maybe supplied to the still 313, or the still may be supplied with tar oroil from some other source. The vapors from the still may be condensedseparately in condensers 322 and 323, or by by-passing the gases thruthe pipe 318 they may be combined with the gases and vapors passing thruthe pipe 305 and condensed and collected together 'with the vaporsdirect from the rich collector main in condensers 307 and 308.

The invention is not limited to the disclosure of the drawings. Fig. 1shows apparatus for distilling with hot gases directly, withoutscrubbing. Fig. 3 shows apparatus for distilling with either rich orlean gases and provides for scrubbing the gases prior to their enteringthe still. With appropriate modifications the equipment shown may berearranged for passing either rich or lean gases directly to the stillwithout scrubbing, or a composite of the gases passing thru the usualcollector main comprising gases from ovens of varying ages, i. e., bothrich and lean gases as in Fig. 1, may be scrubbed prior to theirentrance into the still. Either the still or the scrubber may be heatedexternally, or a heat exchanger of a different type may be provided, inwhich the gases are heated externally while passing thru the connectinggas mains or conduits, or heat may be applied at more than one place, asat both the scrubber and the still or at the preheater, as in Fig. 3.

The still 13 may be replaced by a tower as illustrated in Fig. 9 of thedrawings, wherein the tar or other material to be distilled is permittedto fiow downwardly over a plurality of battles so as to expose largesurfaces of the tar to the hot gases ascending thru the tower and withexternal heating of the tower to aid the distillation. In this way,advantage can be taken of the heating effect of the gases to distill thetar without retarding the gases or causing any appreciable back pressureor greatly disturbing the balance oi gaseous pressures in the system.

Referring to Fig. 9, '71 indicates a tower which may be of any suitableform and construction, and with heating means such as a Jacket thruwhich gases such as the hot flue gases may. if desired, pass to maintainthe desired temperature. The tar accumulated in the decanters 12, 12' or38, or pitch, tar or oil from another source, is delivered thru an inletpipe '72 to the top of the tower and flows downwardly over a pluralityof baiiles 73 arranged therein to facilitate the exposure ot the maximumsurface oi the tar or other material to be distilled to the ascendinggases. These gases may be withdrawn from the collector main anddelivered thru the pipe 14 shown in Fig. 1 to the inlet 74 at the baseof the tower 71. The gases circulate upwardly around the bailies 73,giving up their heat to the descending stream of tar, and escape thru anoutlet 75 which may, for example, be connected to the pipe 16 shown inFig. l. The residue from the tar or oil which accumulates in the bottomof the tower '71 is withdrawn thru a pipe 76 which may be connected tothe pipe 26 shown in Fig. 1. A portion of the tar can be recirculated bya pump '73 thru the pipe '74 to the top of the tower. Since thedescending tar flows over the baffles in relatively thin sheets and isexposed in this form to the hot gases, it interposes the minimumresistance to the flow of the gases. It is, nevertheless, heated by thegases which, depending upon the temperature and other conditions ofoperation, may remove more or less of the volatile constituents from it.These can be condensed as hereinbefore described in connection with thecondensation of vapors from other gases flowing from the ovens, or aseparate condenser system may be utilized to recover any valuableproducts in the gases which leave the still.

Although the operation of the tower in Fig. 9 has been described inconnection with the operation of a system such as that shown in Fig. 1,it is to be understood that the apparatus disclosed in Fig. 9 and alsothe apparatus disclosed in Fig. 10, which is'to be described below, canbe substituted equally well in other systems, such as that shown in Fig.3. The towers may be equipped with jackets appropriate for conductingflue gases, or other means for applying heat externally may be provided.

In the modified form 01' still shown in Fig. 10, the operation issimilar to that in the still shown in Fig. 9, except that instead ofcoming into intimate contact with the hot gases by passing over bailleplates, the pitch, tar or oil is sprayed into the hot gases which areintroduced thru the inlet 80. On ascending thru the tower, the hot gasesvolatilize the. low boiling constituents oi! the liquid which isintroduced thru the spray nozzles 81 so that these constituents arevolatilized, and depending upon the temperature and quantity of thegases, etc., the higher boiling constituents may be volatilized. Thetreated tar or pitch or oil residue collects in the reservoir 82 in thebottom of the tower and may be drawn off continuously or at intervalsthru the outlet pipe 83, or tar, etc. collecting in the reservoir 82 maybe withdrawn by the pump 84 and carried up thru the pipe 85 and againsubjected to treatment by the hot gases by being sprayed again thru thenozzles 81. Instead of recirculating the tar, the nozzles may besupplied with fresh tar introduced thru pipes 83 or tar may beintroduced to the nozzles thru pipes 83' and 85 at one time, or by usingseparate feed pipes certain nozzles may be supplied with treated tar orpitch while other nozzles are supplied with fresh tar. Bafiles 86 orother means may be provided to remove entrained liquor trom the vaporsescaping thru the outlet 87. The towers may be operated on a batchbasis, or they may be operated continuously.

The amount of distillation which takes place within the still willdepend upon the relative quantities and temperatures of the tar andgases and upon the amount of external heat supplied, as by the hot fluegases. The hot coke oven gases for the still may be drawn ofi from theend of the collector main as shown in the drawings, or from any otherpart of the collector main, or other collecting means, or the hot gasesmay be tapped off the cross-over main, or any other part of theapparatus from which gases of desired temperature may be obtained. Thetemperature of the gases will depend upon the part of the apparatus fromwhich the gases are obtained and upon the operation of the coke ovensystem. If spraying is eliminated or kept at a minimum in the uptakes atone end of the collector main, and in the mains, and gases from this endof the collector main are led to the still, these gases will be atalmost the maximum temperature at which the gases enter the collectormain.

Tars, oils or pitches of various grades may be used as ascrubbing'medium and by scrubbing with other pitches, tars or oils thanthose recovered from a coke oven system with hot coke oven gases,composite heavy tars or pitches will be recovered in the scrubber, andcomposite products may be recovered on condensing the vapors from thegases leaving the still. By omitting the scrubbing operation or byproper selection of the tar or oil to be used in the scrubber and thestill, and by regulation of the temperature, the properties of theresulting products can be modified to suit the particular requirementsof the trade.

The combined distillation operation of the present invention with directheating and distillation by the hot coal distillation gases and indirectheating externally, e. g., by waste flue gases, enables the coaldistillation gases to be used more efiectively and at a lowertemperature than when they alone are relied upon for the heating anddistillation. In gas retort or coke oven plants where the coaldistillation gases are cooled in the uptake pipes, collector main, etc.,to a temperature such that effective distillation with the heat contentof the gases would be limited, the external heating of the still makesthe action of the coal distillation gases more effective, enablingellective distillation to be carried out at a relatively lowtemperature.

I claim:

1. In combination with a coke oven battery, a tar still, means connectedwith the waste gas flue from the battery adapted to circulate hot fluegases in indirect heat interchange relation with the contents of thestill, a condenser adapted to condense vapors passing from the still, agas scrubber, and means to collect gases from its a plurality of theovens and pass them directly thru the scrubber into the still.

2. In combination with a coke oven battery, a tar still, a condenseradapted to condense vapors passing from the still, a gas scrubber, meansconnected with the waste gas flue from the battery adapted to circulatehot flue gases in indirect heat interchange relation with the contentsof the still, and means to collect gases from a plurality of the ovensand pass them directly thru the scrubber into the still.

3. The improvement in the method of producing pitch by the distillationof heavy hydrocarbon material in liquid form, which comprises heatingexternally a still containing such material, scrubbing Iresh hot coaldistillation gases with pitchproduced by the distillation of thehydrocarbon material, passing the scrubbed gases thru the still indirect and intimate contact with said material therein so as to producepitch therefrom, and condensing oils distilled therefrom together withoils present in the hot gases in vapor form.

4. The improvement in the method oflproducing pitch from heavyhydrocarbon material in liquid form, which comprises scrubbing fresh hotcoal distillation gases with pitch of substantially the same compositionas that carried in suspension in the gases, passing the scrubbed gasesthru a still in direct and intimate contact with the heavy hydrocarbonmaterial being distilled, simultaneously heating the still externallywhereby the heavy hydrocarbon material is distilled to pitch, andcondensing oils distilled from the hydrocarbon material together withoils present in the gases entering the still.

5. In combination with a coke oven battery a tar still, means connectedwith the waste gas flue from the battery adapted to circulate hot fluegases in indirect heat interchange relation with the contents of thestill, a condenser adapted to condense vapors passing from the still,and means to collect gases from a plurality of the ovens of the batteryand pass them while still hot into the still.

6. The improvement in the method otproducing pitch by the distillationof heavy hydrocarbon material in liquid form, which comprises heatingexternally the still containing such material, heating a heavyhydrocarbon material and scrubbing fresh hot coal distillation gaseswith the hot hydrocarbon material in liquid form, passing the scrubbedgases through the still in direct and intimate contact with the materialtherein so as to produce pitch therefrom, and condensing oils distilledtherefrom together with oils present in the hot gases in vapor form.

STUART PARMELEE MILLER.

